贵州草海湿地农田渠系水质空间分异特征及影响分析

Spatial characteristics and impact of water quality in agricultural dicth systems of Caohai wetland in the Guizhou plateau,China

为了解草海湿地农田渠系水质现状、空间分异特征及影响因素,于2011年秋季对草海湿地进行大空间尺度的采样,分析了氮磷等理化指标,采用单因子污染指数法和营养状态指数法分别对农田渠系水质和湖泊营养状态进行评价.结果表明,草海湿地农田渠系水质污染严重,多数水质为V类或劣V类,总氮和溶解氧是水体中的主要污染因子;上游水质劣于下游,尤其是上游靠近县城区域的水质最差;多等级排水渠系对氮磷具有一定的截留作用,干渠V级水质好于低级渠系水质;不同的土地利用方式对水质的影响不同,城镇用地>集中式村落>农田;草海湿地水体上、中、下游营养水平分别为中度富营养、轻度富营养和中营养,外源污染物的累积和湖泊营养水平的提高导致其沼泽化,而流域不合理的土地利用结构加剧了沼泽化的进程.

Caohai（N26°49′—26°53′,E104°12′—104°18′） is a typical plateau lake wetland located in the southwestern part of Weining County,Guizhou Province,China.To understand the spatial characteristics and impact of water quality in agricultural dicth systems,water samples were taken at 50 sites in Caohai wetland in Autumn 2011,and dissolved oxygen（DO）,total nitrogen（TN）,total phosphorus（TP）,and so on was examined.In order to identify the main pollution loading types of dicth systems,the single factor pollution index was applied.The integrated nutrient status index was also used to judge the trophic status of Lake Caohai.Our results showed that the agricultural dicth system water was polluted seriously,DO and TN were the main polluting factors,and the water quality at most of the locations was Class Ⅴ or worse.The water quality in the upper reach of the Caohai wetland was worse than that in the lower reach.Especially,the water quality in the locations near the towns were the worst.The retention of TN and TP in the agriculture ditches was good,and the water quality in the main channels was much better than that in the agriculture ditches.The impact of the land use patterns on the water quality was in the order of urban land usecentralized villageagricultural area.The nutrition status of the upper,middle and lower reaches of the Caohai wetland was at the level of eutrophication,light-eutrophication and mid-eutrophication,respectively.The accumulation of external pollutants and rise of nutrition status can lead to swampiness,however,an unreasonable land use may facilitate the process of swampiness.